A developer supply device includes a container body that receives and contains a developer with which a toner cartridge is filled and that has a supply port used for supplying the developer, which is contained in the container body, to a developing device, a sensing member that detects the developer contained in the container body, a first transport member that is rotatably disposed in the container body and that transports the developer at a first transport speed by rotating, and a second transport member that is rotatably disposed in the container body in such a manner as to face the sensing member and that transports the developer at a second transport speed that is higher than the first transport speed by rotating.